Internal air assisted brake actuator

ABSTRACT

A spring emergency and parking brake which is further airassisted for added force in the application of the spring emergency brake; that is, there is a combination of air and spring pressure utilized to apply the brakes in an emergency situation when the primary or service air source, normally employed in operating the brakes, fails in one way or another. The source of the air-assisting force is internal to the brake actuator housing and derives from the air used to compress the emergency spring.

United States Patent Swander, Jr. et al. 1 Jan. 23, 1973 [54] INTERNALAIR ASSISTED BRAKE 3,229,539 1 1966 Langas ....91/422 ACTUATOR 3,232,1802/1966 Deschenes..... ....91/422 [75] Inventors: Kenneth D. Swander,Jr., Prairie 1 3 2 3 23 2232i Vlllage; Ronald Over 3,316,817 5/1967E1115 ....91 422 x land Park, both of Kans- 3,331,291 7/1967 Rumsey..92/64 3,479,927 1l/l969 Woodward ..92/64 1 ee: Certain-FeedPrgductsgmration, 3,065,997 11 1962 Frankhouser et a1 ..92 64 Ardmore,Pa. 3,090,359 5/1963 Hoppenstand ..92/64 X 22 F1 d: n 1 1971 1 e PrimaryExaminerMartin P. Schwadron 1 PP 148,921 Assistant Examiner-A.Hershkovitz Related u.s. Application Data Smfield [63] Continuation ofSer. No. 782,131, Dec. 9, 1968, [57] ABSTRACT abandoned' A springemergency and parking brake which is [52] U S Cl 92/63 92/64 92/130further air-assisted for added force in the application lslno 267/65 ofthe spring emergency brake; that is, there is a com- [51] Int Cl "F",7/00 Folb 21/02 bination of air and spring pressure utilized to applythe [58] 1 92/62 64 130; brakes in an emergency situation when theprimary or 91/416 267/65 65 65 R 65 3; service air source, normallyemployed in operating the PM brakes, fails in one way or another. Thesource of the air-assisting force is internal to the brake actuator [56]References Cited housing and derives from the air used to compress theemergency sprmg. UNITED STATES PATENTS 34 Claims, 3 Drawing Figures3,302,530 2/1967 Dobrinkin et a1 ..92/63 X 3,065,997 5/1963 Hoppenstand..92/64 X 7 73a 85a x U, I

e? 9e i Q11 /00 9.3 r 9? 99 R F ;:2

a 2 9/ l I y 961 m3 m2 943C196 90 92 J a9 W t I I I11 I l I I, 5 88 I I9 E I 94 7 figo 0! /04 E I07 5 I08 1 I 109 E BACKGROUND AND SUMMARY OFTHE INVENTION The patent to Hoppenstand, US. Pat. No. 3,090,359, issuedMay 21, 1963, Double Air Chamber Brake Cylinder disclosed (FIG. 4) theuse of a supplemental air source to assist a spring emergency brake.

In the normal operation of air brakes for trucks, buses, trailers andthe like, the service brake, usually a diaphragm acting on a brake rod,is designed to work at 60 percent of the gross weight of the vehicle onthe axle. For a secondary stopping force, that is, the emergency spring,per cent retarding force is usually regarded as adequate. For parkingthe vehicle, a 20 per cent retarding force is regarded to be adequate inorder to be able to handle a 20 per cent grade.

It is considered highly desirable to be able to provide a secondary stopmeans which will be at least 80 per cent as effective as the servicebrake or provide a retardation force equal to 48 percent of the vehicleweight. It is thus that the air-assist concept has come into being to beused in combination with the spring emergency effect. To utilizeair-assist in combination with the spring emergency systems available inthe past, such as Hoppenstand, there must be provided an isolatedreservoir of air. The amount of the supercharge thereof and the placethe supplementary air is put must be independent of the basic airsystem. Valving and lines further must be provided wherein switchingarrangements are available to charge the isolated air assist reservoirsand thereafter transfer this emergency air from its storage place to thebrake actuator.

OBJECTS OF THE INVENTION An object of the instant invention is toprovide an air-assist function in a spring emergency and parking brakeactuator which provides an additional force output to the spring brakeactuator during an emergency stop.

Another object of the invention is to provide an airassist function in aspring emergency and parking brake construction which is entirelyinternal to the spring emergency and parking brake actuator and neitherhas nor requires any external piping, valves or reservoirs whatsoever.

Another object of the invention is to provide an airassist function fora spring emergency and parking brake actuator which gives an additionalforce output for emergency stopping without an increase in the actuatorsize, and without the use of additional air lines or controls.

Another object of the invention is to provide a spring emergency andparking brake actuator which is capable of being interchanged withexisting actuators and systems yet wherein there is additionallyprovided a supercharge of the emergency stop cycle with air.

A further object of the invention is to provide means and methods fordecreasing the system response time in an emergency situation in avehicle utilizing a spring emergency and parking brake actuator system.

Another object of the invention is to provide a spring emergency andparking brake actuator construction wherein the air assist function isadditive thereto, yet

wherein exterior road contamination is entirely prevented from enteringthe spring cavity, whereby to improve seal and spring life.

Another object of the invention is to provide internal means forproviding an air assist function to a spring emergency and parking brakeactuator, whereby less expensive and lighter output power springs may beemployed in the said actuator whereby to provide a safer brake means,under empty conditions.

Still another object of the instant invention is to provide an airassist function in a spring emergency and parking brake actuator whichprovides a stopping force which is great at first, then gradually slacksoff as the speed of the vehicle decreases, much as a high speedcontrolled stop is preferably conducted in automotive vehicles. Thishigher force provides high deceleration at high speeds where high energylevels prevail and thus decreases stop distance.

A further object of the instant invention is to provide an air-assistfunction completely enclosed within the housing or body of a springemergency and parking brake actuator wherein the air pressure from thebasic air system used to compress the power spring is also used tocharge the air-assist function; then, when normal air is lost from thebasic air brake system, the charged air-assist chamber provides anair-assisted spring emergency stop in a controlledmanner.

Other and further objects of the invention appear in the course of thefollowing description thereof.

In the drawings, which form a part of the instant application and let itbe read in conjunction therewith, embodiments of the invention are shownand, in the various views, like numerals are employed to indicate likeparts.

FIG. 1 is a cross sectional view of an add-on spring emergency andparking brake actuator to which has been added the internal air assistfunction which comprises the instant invention.

FIG. 2 shows the subject internal air assisted brake actuator in theform wherein the spring emergency chamber is positioned inboard of theservice chamber.

FIG. 3 shows a detailed view of the check valve mounted in the piston ofFIG. 2.

THE BASIC ADD-ON BRAKE ACTUATOR CONSTRUCTION (FIG. 1)

The general intent of all spring brake actuators is to provide a meansfor applying the foundation service brakes on one or more axles of thevehicle when same has lost its normal air pressure required to operatethe service brake chamber. Under these conditions, it is consideredoperating an emergency brake. When the air pressure that is introducedto the springmechanism air chamber is controlled by the driver and onlyexhausted after a vehicle is brought to a stop with its service brakes,then it is considered a parking brake.

"Add-on units are basically spring brake chambers that are attached to aportion of the existing service brake chamber that is already mounted onthe vehicle. The add-on type transfers the spring force through a sealedinterwall, thence to the pressure side of the normal service brakediaphragm, then through the push rod and foundation brake mechanism tothe brake shoes, whether it is a cam or a wedge brake mechanism. We willfirst describe the basic add-on actuator and then our improvements asapplied thereinto.

Howze U.S. Pat. No. 2,854,954 issued Oct. 7, 1958 for Vehicle BrakeOperating Mechanism shows the fundamental Add-On or Piggy-back typespring emergency and parking brakes.

Referring, then to FIG. 1, at is seen the cylindrical side wall of aspring brake housing. In the view as seen in the drawing, downwardlytherein is toward the axle or inwardly of the brake actuator system andupwards in the view is outwardly of the brake actuator system or awayfrom the vehicle axle or brake drum. The outer wall, then, of the springemergency housing 10 is seen at 11. It is preferably slightly dishedcentrally as at 12 and has a central opening therein 13 whereby toreceive an internally threaded fitting 14. Fitting 14 receives aremovable valve body 15 therein carrying centrally thereof vent valve16, to be described. The inner end or skirt 10a of housing 10 isfastened by bolts 17 to the peripheral wall 18 of an interwall 19. Thelater is the inward termination of the spring emergency chamber and theoutward boundary of the service chamber. Peripheral portion 18 ofinterwall 19 has circumferential seal 20 abutting the inner face ofhousing 10. An air input fitting 21 passes air in through passage 22 toreach the pressurization chamber 23 of the emergency spring housing.

Power piston 24 has peripheral skirt 25 thereon carrying pressure seal27 and felt outer ring 26 therein whereby to ride in reciprocatingmotion against the inner face of housing 10. Piston 24 further hascentral hub 28 having a central opening 29 therethrough fixedlyreceiving push rod 30 therein. Push rod 30 may have an internallythreaded recess 31 at the upper or outer end thereof, for receiving fromoutside wall 1 1 an externally threaded rod for a mechanical releasefunction. This is conventional and will not be described. Power spring32 abuts with its outward end the inner face of outer wall 11 and withits inner end the outer face of piston 24. A central opening 33 isprovided through interwall 19 whereby push rod 30 may pass in sealedreciprocating fashion therethrough. Seal 34 and guide bushing 35 areretained by ring 36, seal push rod 30 through opening 33. A suitable pador pressure face 37 is attached to the inner end of rod 30 by screw 38.

Referring now to the service chamber, the inward end 180 of peripheralportion 18 of interwall 19 abuts the outward peripheral surface of aresilient diaphragm 39. The latter is abutted on its inward peripheralface by service chamber housing member 40, the diaphragm and itsabutting flanges being retained by clamp band 41, itself removable.

Diaphragm abutment pad 42 is attached to the outward end of brake rod 43and abuts the inner face of diaphragm 39. Diaphragm return spring 44abuts spring retainer 45 at its outer end and on its inner end facesagainst the end wall 400 of the service chamber member 40. Suitablebolts 46 and washers 46a serveto attach the brake actuator to suitablebrackets on the vehicle.

A fitting, not shown, analogous to passage 22 is provided in interwallperipheral portion 18 whereby to input air from any suitable line sourceto the service chamber. The latter is generally designated 47 and liesbetween the outer face of diaphragm 39 and the inner face of interwall19. An opening 48 is provided centrally of inner wall a of the servicebrake chamber whereby brake rod 43 may pass therethrough to make itsconventional operating connection with the brake elements.

All of the above, with the exception of valve 16 and fittings 15 and 14are characteristic of a typical Add- On spring emergency brake unit asis seen in Howze, supra.

ADD-ON EMERGENCY BRAKE FUNCTION Compressed air to spring chamber 23enters through tapped hole or fitting 21 and air passage 22. Whensufficient pressure of air is present in chamber 23, piston 24 is forcedupwardly or outwardly as shown in FIG. 1. This compresses power spring32 and also brings disc or pressure plate 37 on rod 30 upwardly oroutwardly in the view, close to interwall 19.

When power spring 32 is compressed, the service brake works in thenormal manner, that is, under the influence of air pressure in servicechamber 47 acting on flexible diaphragm 39. When air pressure in chamber47 is increased, diaphragm 39 is forced downwardly or inwardly in theview of FIG. 1, moving push rod 43 and pad 42 whereby to apply thebrake.

Under these conditions, piston 24 and piston rod 30 I remain as shown inFIG. 1. When pressure is reduced in service chamber 47, diaphragm 39moves upwardly or outwardly to the position shown in FIG. l..Push rod 43moves upwardly along with it, forced by diaphragm return spring 44. Thisreleases the brake.

When air is released from chamber 23, the power spring 32 forces piston24, push'rod 30'and pressure plate 37 downwardly in the view of FIG. 1,thereby applying the brakes. The brakes can be released only byreinstating the air pressure in chamber 23 or by using a mechanicalrelease means as has been, in the art and will not be shown or describedhere. Such may be seen in the application of Swander Jr., et al., Ser.No. 520,693, filed Jan. 14, 1966 for Brake Actuator, now abandoned.

THE AIR-ASSIST APPARATUS In a typical add-on unit as seen in Howze,supra or Swander et al., supra, the spring cavity 49 (the space definedbetween the inner face of outer wall 11 and the outer face of piston 24)is usually vented by an opening typically provided in outer wall 11.However, in the instant construction, spring cavity 49 is sealed andthere is no vent provided save for opening 13 which receives fitting 14and valve body 15 therein. There is provided, through valve body 15,passage 15a which is enlarged at its upper end and removably receivesvent valve 16 therein, retained in the upper or outer portion of passage15a by ring 16a. Vent valve 16 typically will open to vent passage 15afrom inside the spring cavity at approximately 35 psi.

A passage 50, internally threaded at its outward or upward end 51, isprovided through piston 24 radially outwardly of hub 28. Removablythreaded into passage 50 is check valve 52 (checking flow from chamber23 into cavity 49). The latter comprises a cylindrical ex-- ternallythreaded fitting having a passage extending thereinto centrally thereoffrom its upper or outer end, the passage blanked at the lower end withoutwardly extending radial ports or passages which are sealed by anO-ring at its lower or inner lesser diameter end.

A second passage 53, also enlarged at its outer or upper end, in theview of FIG. 1, has inlet valve generally designated 54 retained in theenlarged portion therein by retainer ring 55. Inlet valve 54 opens fromspring chamber 23 into spring cavity 49 typically at a pressure of 85psi.

AIR-ASSIST FUNCTION As previously described with respect to the typicalAdd-On or Piggy-Back spring emergency or parking brake function, whensufficient air pressure is introduced through fitting 21 and passage 22into spring chamber 23 in order to release the vehicle parking brakes,the piston moves to the position shown in FIG. 1, namely, compressingthe power spring 32.

After air pressure has risen in chamber 23 to 85 psi (or any optionalpressure desired or dictated by inlet valve 54), inlet valve 54 opens.This allows air in excess of 85 psi (or other set pressure) to enterspring cavity 49.

If air pressure is above 35 psi (or any desired and set limit in theapplication at hand), vent valve16 opens and bleeds off any excesspressure. This feature maintains a controlled pressure charge in thespring cavity. This pressure must be balanced to the pressure availableand the desired design performance of the vehicle.

When an emergency stop situation arises, that is, when air pressure issuddenly lost from spring chamber 23, there is caused a pressureunbalanced situation to exist with respect to piston 24. Air pressureexcess in cavity 49 provides force to assist power spring 32 in making afaster emergency stop.

Check valve 52 opens downwardly or inwardly into the spring chamber 23in the view of FIG. 1 from spring cavity 49. Due to the structure ofcheck valve 52, it takes approximately to seconds to deplete the air inthe spring cavity. This is adequate, when combined with the power spring32 force, to stop a high speed vehicle and result in a stopping forcewhich is great at first, then gradually slacking off as the vehiclespeed decreases. This is considerably analogous to a theoreticallydesired high speed stop in an automobile, fully controlled.

After the air has been bled from the spring cavity 49, the cycle isready for a repeat. It is not necessary to deplete the air, to repeatthe cycle, but there would be required higher air pressure within springchamber 23 before the parking brake could be released. Check valve 52times the back flow.

MAXI ACTUATOR FIG. 2 shows the subject internal air assisted brakeactuator in the form wherein the spring emergency chamber is positionedinboard of the service chamber. An elongate cylindrical housing 60 hasan inner (inward toward the axle or brake mechanism) end 61.

Median wall 73 divides the service chamber from the spring emergencychamber. Wall 73 has central opening therein 74 with O-ring 75positioned centrally of the passage of the opening. A brake rod 76 hasfixed to one end thereof pad 77 and extends through opening 74 with seal75 hearing there against. Return spring 78 bears at its inward endagainst wall 73 and at its outer end against spring retainer 79.

On the inward side of wall 73, peripheral to opening 74 there isprovided our spring retaining flange 80. The outer flange 73 a of wall73 is fixed centrally of housing 60 by spaced screws or bolts 81 and hasa circumferential seal 82 in circumferential groove 83 in the outer orperipheral face thereof. Wall 73 also is tapped as at 84 to receivethreaded fitting 85 which also passes through opening 86 in housing 60.Power spring 87 bears at its outward end against the inward surface ofwall 73 and at its inner end against the outward surface of power piston88. Piston 88 has peripheral skirt 89 with seal 90 and lubricating ring91 in circumferential grooves 92 and 93, respectively. Central of piston88, there is provided outwardly dished portion 94 having one threadedopening 95 positioned in the central portion thereof and a non-threadedpassage 96 therewithin having lesser diameter inward portion 97connected thereto. The outer central portion of piston 88 in ring 98 hasO-ring seal 99 received in circumferential groove 100. A hollow tube 101is fixed by suitable means at 102 to piston 88 inwardly and centralthereof. Flexible joint 103 connects brake rod 76 with its extension 104passing through tube 101 and having externally threaded portion 105 uponwhich is threaded nut 106.

Fitting 107 having opening 108 therethrough is received in housing 60adjacent the inward end thereof. Bolts 109 and 110 havingcircumferential seals 111 and 1 12, respectively, are received inopenings 1 13 and 114 in housing end 61. Ring 115 is received withinopening 63 and has seal 116 sealing said opening and seal 117 sealingagainst the outer surface of tube 101.

Included among the advantages of the brake actuator of FIG. 2 withrespect to the brake actuator FIG. 1 are the possibilities of all steelstructure in the type actuator of FIG. 2, whereas wall 19 in FIG. 1 isdie-cast material. Further, the actuator of FIG. 2 has relativelysmaller length than that of FIG. I which is required in certainapplications where space is important. Yet, further, any defect in themounting of the brake actuator caused by any means results in settingoff the spring brake, whereby a fail safe unit is provided. Further, inthe event of failure of an add-on type unit at the clamp band 41, theentire unit would escape the vehicle which results in the loss of boththe service and emergency brake functions. Finally, the servicediaphragm is accessible without disturbing the rest of the brake in thestandard-type brake of FIG. 2.

AIR ASSIST FUNCTION IN MAXI ACTUATOR When sufficient air pressure isintroduced, referring to FIG. 2, into fitting 107 and passage 108 intothe spring chamber between the inner end of the housing 61 and thepiston 88, the piston moves to the position shown in FIG. 2, namely,compressing the power spring 87.

After air pressure has risen in the chamber 120 to 85 psi (or anyoptional pressure desired or dictated by inlet valve 96), this allowsair in excess of 85 psi (or other set pressure) to enter spring cavity121.

If air pressure is above 35 psi (or any desired and set limit in theapplication at hand), vent valve 85a opens and bleeds off'any excesspressure. This feature maintains a controlled pressure charge in thespring cavity 121. The pressure must be balanced to the pressureavailable and the desired design performance of the vehicle.

When an emergency stop situation arises, that is, when air pressure issuddenly lost from spring chamber 120, there is caused a pressureunbalanced situation to exist with respect to piston 88. Air pressureexcess in cavity 121 provides force to assist power spring 87 in makinga faster emergency stop.

Check valve 950 opens downwardly or inwardly into the spring chamber 120in the view of HO. 2 from spring cavity 121. Due to the structure ofcheck valve 95a, it takes approximately to seconds to deplete the air inthe spring cavity 121. This is adequate, when combined with the powerspring 87 force, to stop a high speed vehicle and result in a stoppingforce which is great at first, then gradually slackening off as thevehicle speed decreases. This is considerably analogous to atheoretically desired high speed stop in an automobile, fullycontrolled.

After the air has been bled from the spring cavity 12], the cycle isready for a repeat. It is not necessary to deplete the air, to repeatthe cycle, but there would be required higher air pressure within springchamber 120 before the parking brake could be released. Check valve 95atimes the back flow.

Any regulation of the system pressure, either by selection of govenorsetting or introduction of a pressure regulating valve dictates whetherthe air assist feature would be in effect. That is, referring to the airassist function described with respect to the add-on and maxi actuators,if the air pressure in chambers 23 or 120, in the examples given, neverrises above 85 psi or the optional pressure desired or dictated by theinlet valves 54 or 96a, air will not enter spring cavity 49 or springcavity 121. Any air which does enter the spring cavity above 85 psi, butbelow the psi indicated for the examples where the vent valve 85a or 16open and bleed off will serve to give a limited air assist.

ln modulation of application of the brake within the time period of thecheck valves 52 and 95a (in order to overcome wheel slide), suchmodulation works against the air assist behind the piston.

It is entirely possible to operate the system with the check valves 95aand 52 removed therefrom, and passages 50 and 95 closed off. In suchcase, there is lost the bleed down of the system which removes the airassist effect which aides in the recompression of the spring. When airis input through fitting 108 or opening 22 into cavities 120 and 23,respectively, without the check valves 95a or 52, recompression isagainst residual air in the spring cavity 121 or 49. lf the vent valves85a and 16 are present, the recompression is never against more than the35 psi indicated in the examples in the systems given as examples.

It is further feasible to operate the systems with the vent valves 85aand 16 removed therefrom, but, in such case, it is best that the checkvalves 95a and 52 be present in order that there be a bleed down of theair assist function prior to recompression.

It is desirable thatthe combined spring pressure and air assist functionpressure never exceed the system pressure.

An important feature of this system is that, when the vehicle is loaded,and it is desired to have the maximum effective breaking power, the airin the system which charges chambers 23 and 120 can be maintained at apressure, for the examples given, of 120 lbs. This means that the airassist chamber will be charged over 35 lbs. in the examples given. Oncethe vehicle is unloaded, the system may be controlled by a govenor orthe introduction of a pressure regulating valve to charge no more than85 lbs. through openings 22 or 108 whereby the air assist function wouldnot be operative on a lightly loaded or unloaded vehicle. This wouldprevent wheel skid from excessive brake application. Therefore a degreeof weight control of the braking system is possible by regulating theinput to the chambers 23 and 120 below to pounds on the inlet valves 54and 96a. One may therefore put in or cut out the air assist. Theoperator would be instructed to actuate the govenor or pressureregulating valve when the vehicle was unloaded.

Inlet valves 96a or 54 crack at 75 to 85 lbs., plus or minus 2 lbs.(73-87). Same are semi-adjustable by dropping in a shim. The pressure inthe chambers 121 and 49 are set from 30 to 40 pounds with a tolerance ofplus or minus 2. That is, 28 to 42 lbs. Vent valves 85a or 16 have acracking pressure of 40 lbs., plus 5, minus 0, that is 40 to 45 lbs.before it opens. There is an overlap of 2 lbs. between valve 54 closingand valve 16 opening. Vent valve 16 ranges from cracking pressure downto 20 percent and will close when the pressure in cavity 49 drops 20percent to 31 to 32 lbs.

Check valves a and 52 are back flow timing check valves. They sealbubble tight at plus 2 lbs. and crack at l to 5 lbs. plus or minus 2. (3lbs.) A typical timing rate for the check valves would be 24 seconds toexhaust plus or minus 5 a 75 cubic inch chamber in chambers 121 or 49compressed at 30 psi.

Looking at FIG. 3, valve 95a has thread 95 b on body portion 95c whichhas relatively large diameter opening 122 therethrough which terminatesin lesser diameter dead-end passage 123. A plurality of orifices (fourin number typically) 124 reach outwardly into lesser diameter portion125 of the check valve. A seal-ring 126 fits over the orifices in thegroove 125. Openings 124 are sized to give the throttling effectdescribed immediately above.

SPRINGLESS AlR ASSIST FUNCTION Referring to FIG. 2, it will be seenthat, even with spring 87 removed from cavity 121 in the assembly, thepiston 88 can be moved upwardly in the viewby air input through fitting108, alsoaided by diaphragm return spring 78. An excess of air pressureover that required to actuate inlet valve 96a will cause cavity 121 tofill with pressurized air to the degree the pressure in cavity exceedsthe pressure required to actuate inlet valve 960. Should cavity 120 losepressure from loss of general system pressure and loss of service brakefunction, the piston 88 will be moved downwardly in view of FIG. 2 underthe air pressure contained in cavity 121 to exert a limited airpressurized emergency brake function.

Since the power of the piston with the spring removed would be limitedtotally to what air could be put into chamber 121 over the resistance ofinlet valve 96a there would be no need for the relief or pop valve 85a.Further, while valve 95a, the bleed down valve, would be somewhat usefulin exhausting any residual air chamber 121 pressure after the expansion,such would be of no great significance in the recompression of piston 88back towards bulk head 73 and thus valve 95a could be removed with theopenings which receive them (valves 85a and 95a) sealed. In short, theprovision of a piston 88 in the structure of FIG. 2, with valves 95a and85a removed and their openings sealed and power spring 87 removed wouldalso give air assist effect.

The above remarks apply to FIG. 1 in that, referring to chamber 49, thepower spring 32 could be removed and piston 24 would then be operated bythe air assist function alone by air entering through inlet valve 54from original pressurization of chamber 23 through passage 22. Thespringless chamber 49 will be charged with excess air pressure throughinlet valve 54 after piston 24 has been compressed back to the positionof HG. l, the excess being that of the system over the set pressure ofthe inlet valve 54. When pressure goes out of chamber 23 due to loss ofsystem pressure, the piston 24 moves downwardly in the view of FIG. 1and sets the vehicle brake. In the case of both the add-on andspring-forward actuators of FIG. 1 and FIG. 2 respectively, it may thusbe seen that springless air assist may be achieved in the mannerdescribed. Likewise, in FIG. I, the valves 52 and 16 preferably would beremoved. With respect to the figures previously given with respect tothe relative forces of the spring employed and the air assist in cavityin 49 of 121, it was seen that the spring was a major proportion of theforce used and the air assist portion a relatively lesser same. However,without these springs, it is possible to adjust inlet valve 54 or inletvalve 96a so that the air pressurization into chamber 49 or 121 is up toan amount equal the supply pressure less normal friction and less normalopening and closing pressure range of the inlet valves, and any residualpressure in chamber 49 or 121. The spring 32 and 87 strength values maybe varied as desired from the relatively heavy values of the earlierexamples of FIGS. 1 and 2 to a very low value depending primarily on theair assist function.

In all of the forms discussed, it should be understood that diaphragmscould be substituted for pistons 88 and 24. Discs would have to bereceived through the diaphragm for valve insertions such as 96a, 95a, 54and 52 with the said diaphragms fastened centrally as at 102 and to rod30 in FIG. 1 to perform the functions of the movable piston.

With respect to inlet valves 54 and 96a, spring 32 or 57 plus the inletvalve 96a or 54 value plus lbs. equals the supply pressure to chamber23. The setting of the vent valves 16 and 85a equals the suppliedpressure minus the inlet valve setting plus 5 lbs. The back flow checkvalves 95a and 52 are variable time depending on the application. Forexample, in an intercity bus, a considerably shorter stop time isrequired than in a truck because same is lighter, slower and people areinvolved.

The application of the springless air assist would be particularly apton a tandem axle truck, for example, where no brake is required on thefront axle and braking units apply to the two rear axles. One of therear axles could employ the springless air assist (no power spring 32and 87 in the two brake units) while the other axle could employ bothair assist and spring as in FIGS. 1 or 2. In this manner, requirementsfor primary braking (diaphragms 39 and 69), enhanced secondary braking(pistons 24 and 88 with and without power springs) and parking (pistons24 and 88 and springs 32 and 87) will be satisfied.

A wedge brake installation has two floating shoes which can be actuatedby (1) two service chambers, (2) two spring emergency chambers as inFIG. 1 or 2, or (3) one of each. ln the case of number 2, one of thesecould be a springless air assist chamber, the other air assist withspring. The latter case gives the parking function as well as primaryand secondary braking functions.

From the foregoing, it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forthtogether with other advantages which are obvious and which are inherentto the structure.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcomninations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

We claim:

1. In a brake actuating device having spring emergency and parkingfunctions and having operable connection with the braking mechanism of amotor vehicle and comprising,

a closed housing divided into inner and outer compartments,

a flexible diaphragm peripherally secured in the outer compartment,

a brake operating rod surmounted by a diaphragm abutment plate extendingaxially through the inner and outer compartments and having attachmentto the braking mechanism,

a movable wall mounted within the inner compartment equipped with atubular axial extension surrounding and having abutting engagement atits inner end with said rod,

an annular member forming the partition between the inner and outercompartments,

a power compression spring unit between said annular member and movablewall,

a rod return compression spring between the diaphragm abutment plate andannular member;

separate air inlets for introducing compressed air to the innercompartment between the movable wall and the inner end of the housingand to the outer compartment between the diaphragm and the outer end ofthe housing,

the improvements which comprise said movable wall, centrally thereof,slidingly sealed in pressure retaining fashion to the brake operatingrod,

said annular member also slidingly sealed in pressure retaining fashionto said brake operating rod,

said annular member and movable wall seals on the brake operating rod,together with the member and wall, defining therebetween a sealed airassist chamber,

the tubular axial extension of the movable wall extending through theinner end of the housing in sliding sealed fashion whereby to defineperipherally thereof within the housing and between the inner end of thehousing and the inner face of the movable wall a movable wallpressurization chamber,

at least one passage through said movable wall having inlet valve meanspermitting air flow from the movable wall pressurization chamber intothe air assist chamber when the pressure in the movable wallpressurization chamber reaches a certain predetermined level, and

check valve means therein checking flow from the movable wallpressurization chamber into the air assist chamber and permitting flowin opposite direction under certain conditions.

2. A brake actuating device as in claim 1 including a vent valve fromthe air assist chamber exterior of said closed housing operative to ventpressure from said air assist chamber outside of said housing at apredetermined pressure level within said air assist chamber 3. A deviceas in claim 1 wherein the check valve means and the inlet valve meansthrough the movable wall communicating between the air assist chamberand the movable wall pressurization chamber are positioned withinseparate passages through said movable wall.

4. In combination,

a housing,

said housing having inner and outer ends with respect to a vehicle brakemechanism,

one end of said housing closed by an inner wall member having a centralopening therethrough,

the other end of said housing closed by an outer wall member,

a movable wall within said housing with the outer face thereof next tothe outer wall member of said housing,

coil compression spring means seating between said movable wall outerface and housing outer wall member,

a rod connected at one end thereof centrally of said movable wall,extending inwardly of the latter and having a sliding fit through theinner wall member central opening,

an air inlet into said housing between the inner wall member and theinner face of the movable wall whereby to permit pressurization of amovable wall pressurization chamber defined between said movable walland inner wall member,

the movable wall outer face and outer wall member defining therebetweenan air assist chamber,

at least one opening through said movable wall communicating from saidmovable wall pressurization chamber to said air assist chamber andhaving inlet feed valve means operative at a predetermined pressurelevel to pass air pressure from said movable wall pressurization chamberinto said air assist chamber, and

check valve means therein checking flow into the air assist chamber andpermitting flow therefrom under certain conditions.

5. A device as in claim 4 including a relief valve in said outer wallmember operative to relieve the air assist chamber defined between themovable wall outer face and outer wall member atta predeterminedpressure therein.

6. A device as in claim 4 wherein the check valve means and the inletvalve means through the movable wall communicating between the airassist chamber and the movable wall pressurization chamber arepositioned within separate passages through said movable wall.

7. Brake actuating mechanism comprising a closed housing having innerand outer walls, said walls inner and outer with respect to a vehiclebrake mechanism,

a flexible diaphragm within said housing peripherally secured in place,

means for introducing fluid under pressure to said housing adjacent theouter wall thereof and on the outer side of said diaphragm,

a brake operating rod on the other, inner side of said diaphragm axiallyarranged relative thereto,

said rod projecting through the inner end wall of the housing forreciprocatory movements,

a pad on the outer end of said brake or rod operable to bear againstsaid diaphragm an auxiliary compartment at one end of said housing,

the outer end wall of said housing constituting the inner end wall ofsaid compartment,

the inner end wall of the compartment having a central openingtherethrough,

the outer end of said compartment closed by an outer wall member,

a movable wall within said compartment with the outer face thereoffacing the outer wall of said compartment,

coil compression spring means seating between said movable wall outerface and compartment outer wall member,

a rod connected centrally with said movable wall, ex-

tending inwardly thereof and having a sliding fit through the housingouter end wall central openmg,

means for introducing fluid under pressure to said compartment adjacentto the housing outer wall for normally holding the movable wall in theregion of the compartment outer wall thereby to hold said coilcompression spring means under compression,

said fluid under pressure introduced into a movable wall pressurizationchamber between the movable wall inner face and the housing outer wallouter face,

at, least one passage through said movable wall connecting the movablewall pressurization chamber and the air assist chamber with check valvemeans therein checking flow from the movable wall pressurization chamberto the air assist chamber while permitting flow in the other directionunder certain pressurization conditions and inlet valve means operativeto pass fluid under pressure from the movable wall pressurizationchamber to the air assist chamber when the pressure level within themovable wall pressurization chamber rises above a predetermined level.

8. A brake actuating mechanism as in claim 7 including a vent valve inthe outer end wall of said compartment operative to vent the air assistchamber defined by the movable wall outer face and the inner face of thecompartment outer wall.

9. A device as in claim 7 wherein the check valve means and the inletvalve means through the movable wall communicating between the airassist chamber and the movable wall pressurization chamber arepositioned within separate passages through said movable wall.

10. In a brake actuating device having spring emergency and parkingfunctions, operable connection with the braking mechanism of a vehicleand comprising,

a closed housing divided into inner and outer compartments, flexiblediaphragm peripherally secured in the outer compartment,

a brake operating rod surmounted by a diaphragm abutment plate extendingaxially through the inner and outer compartments and having attachmentto the braking mechanism,

a movable wall mounted within the inner compartment equipped with atubular axial extension surrounding and having abutting engagement atits inner end with said rod,

an annular member forming the partition between the inner and outercompartments,

a power compression spring unit between said annular member and movablewall,

a rod return compression spring between the diaphragm abutment plate andannular member, separate air inlets for introducing compressed air tothe inner compartment between the movable wall and the inner end of thehousing and to the outer compartment between the diaphragm and the outerend of the housing,

the improvements which comprise said movable wall, centrally thereof,slidingly sealed in pressure retaining fashion to the brake operatingrod,

said annular member also slidingly sealed in pressure retaining fashionto said brake operating rod,

said annular member and movable wall seals on the brake operating rod,together with the member and wall, defining therebetween a sealed airassist chamber,

the tubular axial extension of the movable wall extending through theinner end of the housing in sliding sealed fashion, whereby to defineperipherally thereof within the housing and between the inner end of thehousing and the inner face of the movable wall a movable wallpressurization chamber,

at least one air flow passage having inlet valve means therewithinpermitting air flow from the movable wall pressurization chamber intothe air assist chamber, when the pressure in the movable wallpressurization chamber reaches a certain predetermined level.

II. A device as in claim 10 including check valve means in a passagecommunicating between the movable wall pressurization chamber and airassist chamber checking air flow from the movable wall pressurizationchamber into the air assist chamber and permitting air flow in oppositedirection under certain conditions.

12. A brake actuating device as in claim 10 including a vent valve fromthe air assist chamber exterior of said closed housing operative to ventpressure from said air assist chamber outside of said housing at apredetermined pressure level within said air assist chamber.

13. A device as in claim 10 wherein the check valve means and the inletvalve means communicating between the air assist chamber and the movablewall pressurization chamber are positioned within separate passages.

14. A brake actuating device as in claim 11 including a vent valve fromthe air assist chamber exterior of said closed housing operative to ventpressure from said air assist chamber outside of said housing at apredetermined pressure level within said air assist chamber.

15. In combination,

a housing,

said housing having inner and outer ends with respect to a vehicle brakemechanism,

one end of said housing closed by an inner wall member having a centralopening therethrough,

the other end of said housing closed by an outer wall member,

a movable wall within said housing with the outer face thereof next tothe outer wall member of said housing,

coil compression spring means seating between said movable wall outerface and housing outer wall member,

a rod connected at one end thereof centrally of said movable wall,extending inwardly of the latter and having a sliding fit through theinner wall member central opening,

an air inlet into said housing between the inner wall member and theinner face of the movable wall, whereby to permit pressurization of amovable wall pressurization chamber defined between said movable walland inner wall member,

the movable wall outer face and outer wall member defining therebetweenan air assist chamber, and

at least one air flow passage communicating between said movable wallpressurization chamber and said air assist chamber and having inlet(feed) valve means positioned therein operative at a predeterminedpressure level to pass pressurized air from said movable wallpressurization chamber into said air assist chamber( when, and onlywhen, the fluid pressure in said chamber exceeds a predetermined levelwhich is beyond that required to compress the power spring,

but to prevent flow in the opposite direction and thereby provide aforce tending to move the movable wall to apply the brake upon reductionof pressure in the chamber into which the supply of pressure fluid isnormally introduced.

16. A device as in claim 15 including check valve means in a passagecommunicating between the movable wall pressurization chamber and airassist chamber checking air flow into the air assist chamber from themovable wall pressurization chamber and permitting air flow therefromunder certain conditions.

17. In combination,

a housing,

said housing having inner and outer ends with respect to a vehicle brakemechanism,

one end of said housing closed by an inner wall member having a centralopening therethrough,

the other end of said housing closed by an outer wall member,

a movable wall within said housing with the outer face thereof next tothe outer wall member of said housing,

coil compression spring means seating between said movable wall outerface and housing outer wall member,

a rod connected at one end thereof centrally of said movable wall,extending inwardly of the latter and having a sliding fit through theinner wall member central opening,

an air inlet into said housing between the inner wall member and theinner face of the movable wall, whereby to permit pressurization .of amovable wall pressurization chamber defined between said movable walland inner wall member,

the movable wall outer face and outer wall member defining therebetweenan air assist chamber, and

at least one air flow passage communicating between said movable wallpressurization chamber and said air assist chamber and having inlet feedvalve means therein operative at a predetermined pressure level to passpressurized air from said movable wall pressurization chamber into saidair assist chamber(.)

check valve means in a passage communicating between the movable wallpressurization chamber and air assist chamber checking air flow into theair assist chamber from the movable wall pressurization chamber andpermitting air flow therefrom under certain conditions, and

(A device as in claim including) a relief valve operative to relieve theair assist chamber defined between the movable wall outer face and outerwall member at a predetermined pressure therein.

18. In combination,

a housing,

said housing having inner and outer ends with respect to a vehicle brakemechanism,

one end of said housing closed by an inner wall member having a centralopening therethrough,

the other end of said housing closed by an outer wall member a movablewall within said housing with the outer face thereof next to the outerwall member of said housing,

coil compression spring means seating between said movable wall outerface and housing outer wall member,

a rod connected at one end thereof centrally of said movable wall,extending inwardly of the latter and having a sliding fit through theinner wall member central opening,

an air inlet into said housing between the inner wall member and theinner face of the movable wall, whereby to permit pressurization of amovable wall pressurization chamber defined between said movable walland inner wall member,

the movable wall outer face and outer wall member defining therebetweenan air assist chamber, and

at least one air flow passage communicating between said movable wallpressurization chamber and said air assist chamber and having ,inletfeed valve means therein operative at a predetermined pressure level topass pressurized air from said movable wall pressurization chamber intosaid air assist chamber(.), and

(A device as in claim 19 including) a relief valve operative to relievethe air assist chamber defined between the movable wall outer face andouter wall member at a predetermined pressure therein.

19. Brake actuating mechanism comprising a closed housing having innerand outer walls,

said walls inner and outer with respect to a vehicle brake mechanism,

a flexible diaphragm within said housing peripherally secured in place,

means for introducing fluid under pressure to said housing adjacent theouter wall thereof and on the outer side of said diaphragm,

a brake operating rod on the other, inner side of said diaphragm axiallyarranged relative thereto,

said rod projecting through the inner end wall of the housing forreciprocatory movements,

a pad on the outer end of said brake or rod operable to bear againstsaid diaphragm,

an auxiliary compartment at one end of said housing,

the outer end wall of said housing constituting the inner end wall ofsaid compartment,

the inner end wall of the compartment having a central openingtherethrough,

the outer end of said compartment closed by an outer wall member,

a movable wall within said compartment with the outer face thereoffacing the outer wall of said compartment,

coil compression spring means seating between said movable wall outerface and compartment outer wall member, I

a rod connected centrally with said movable wall, ex-

tending inwardly thereof and having a sliding fit through the housingouter end wall central opening,

means for introducing fluid under pressure into a movable wallpressurization chamber between the movable wall inner face and thehousing outer wall outer face, thus normally holding the movable wall inthe region of the compartment outer wall thereby to hold said coilcompression spring means under compression,

a passage interconnecting the movable wall pressurization chamber andthe air assist chamber;

inlet valve means in said passage so positioned and so functioning as topass fluid under pressure from the movable wall pressurization chamberto the air assist chamber when and only when the pressure level withinthe movable wall pressurization chamber rises above a predeterminedlevel which is beyond that required to compress the power spring,

but to prevent flow in the opposite direction and thereby provide aforce tending to move the dividing wall to apply the brake uponreduction of pressure in the compartment into which the supply ofpressure fluid is normally introduced.

20. A device as in claim 19 including check valve means in a passageinterconnecting the movable wall pressurization chamber and the airassist chamber checking air flow from the movable wall pressurizationchamber to the air assist chamber while permitting air flow in the otherdirection under certain pressurization conditions.

21. A brake actuating mechanism as in claim 19 including a vent valveoperative to vent to atmosphere the air assist chamber (defined by themovable wall outer face and the inner face of the compartment outerwall) at a predetermined pressure level therein.

22. In a brake actuating device having emergency and parking functions,operable connection with the braking mechanism of a vehicle andcomprising,

a closed housing divided into inner and outer compartments,

a flexible diaphragm peripherally secured in the outer compartment,

a brake operating rod surmounted by a diaphragm abutment plate extendingaxially through the inner and outer compartments and having attachmentto the braking mechanism, 1

a movable wall mounted within the inner compartment equipped with atubular axial extension surrounding and having abutting engagement atits inner end with said rod,

an annular member forming the partition between the inner and outercompartments,

a rod return compression spring between the diaphragm abutment plate andannular member,

separate air inlets for introducing compressed air to the innercompartment between the movable wall and the inner end of the housingand to the outer compartment between the diaphragm and the outer end ofthe housing,

the improvements which comprise said movable wall, centrally thereof,slidingly sealed in pressure retaining fashion to the brake operatingrod,

said annular member also slidingly sealed in pressure retaining fashionto said brake operating rod,

said annular member and movable wall seals on the brake operating rod,together with the member and wall, defining therebetween a sealed airassist chamber,

the tubular axial extension of the movable wall extending through theinner end of the housing in sliding sealed fashion, whereby to defineperipherally thereof within the housing and between the inner end of thehousing and the inner face of the movable wall a movable wallpressurization chamber,

at least one air flow passage having inlet valve means therewithinpermitting air flow from the movable wall pressurization chamber intothe air assist chamber, when the'pressure in the movable wallpressurization chamber reaches a certain predetermined level.

23. A device as in claim 22 including check valve means in a passagecommunicating between the movable wall pressurization chamber and airassist chamber checking air flow from the movable wall pressurizationchamber into the air assist chamber and permitting air flow in oppositedirection under certain conditions.

24. A device as in claim 22 including a vent valve from the air assistchamber exterior of said closed housing operative to vent pressure fromsaid air assist chamber outside of said housing at a predeterminedpressure level within said air assist chamber.

25. A device as in claim 22 wherein the check valve means and the inletvalve means communicating between the air assist chamber and the movablewall pressurization chamber are positioned within separate passages.

26. In combination,

a housing,

said housing having inner and outer ends with respect to a vehicle brakemechanism,

one end of said housing closed by an inner wall member having a centralopening therethrough,

the other end of said housing closed by an outer wall member,

a movable wall within said housing with the outer face thereof next tothe outer wall member of said housing,

a rod connected at one end thereof centrally of said movable wall,extending inwardly of the latter and having a sliding fit through theinner wall member central opening,

an air inlet into said housing between the inner wall member and theinner face of the movable wall, whereby to permit pressurization of amovable wall pressurization chamber defined between said movable walland inner wall member,

the movable wall outer face and outer wall member defining'therebetweenan air assist chamber,

at least one air flow passage communicating between said movable wallpressurization chamber and said air assist chamber and having inlet feedvalve means positioned therein and so functioning as to be operative ata predetermined pressure level to pass pressurized air from said movablewall pressurization chamber into said air assist chamber(.)

when, and only when, the fluid pressure in said compartment exceeds apredetermined level which is beyond that required to compress the powerspring,

but to prevent flow in the opposite direction and thereby provide aforce tending to move the dividing wall to apply the brake uponreduction of pressure in the compartment into which the supply ofpressure fluid is normally introduced.

27. A device as in claim 26 including check valve means in a passagecommunicating between the movable wall pressurization chamber and airassist chamber checking air flow into the air assist chamber from themovable wall pressurization chamber and permitting air flow therefromunder certain conditions.

28. A device as in claim 26 including a (relief) vent valve operative torelieve to atmosphere the air assist chamber (defined between themovable wall outer face and outer wall member of the) at a predeterminedpressure level therein.

29. Brake operating equipment of the kind comprising a brake actuatingmember reciprocable in brake applying and brake releasing directions,

the brake operating equipment being divided into two sectionsrespectively operating as service and emergency braking devices,

the service braking device including a fluid pressure chamber having asupply connection providing for introduction of pressure fluid andhaving a reciprocable fluid pressure responsive wall element forimparting brake applying motion to the brake actuating member,

the equipment being characterized in that the emergency braking deviceincludes a fluid pressure chamber,

a reciprocable element forming a wall dividing the pressure chamber ofthe emergency device into two compartments,

said wall being movable in one direction to effect emergency applicationof the brake,

a supply connection normally providing for introduction of pressurefluid into that one of the compartments in which pressure acting onsaidvwall tends to move the wall in the other direction,

a passage interconnecting said two compartments,

and

an inlet valve in said passage positioned and so functioning as toprovide for fluid flow from said one compartment into the other when,and only when, the fluid pressure in said compartment exceeds apredetermined level which is beyond that required to compress the powerspring,

but to prevent flow in the opposite direction and thereby provide aforce tending to move the dividing wall to apply the brake uponreduction of pres sure in the compartment into which the supply ofpressure fluid is normally introduced.

30. A device as in claim 29 including a vent valve from one of saidcompartments exterior to atmosphere thereof operative to vent pressuretherefrom at a predetermined pressure level within said compartment.

31. Brake operating equipment of the kind comprising a brake actuatingmember reciprocable in brake applying and brake releasing directions,

the brake operating equipment being divided into two sectionsrespectively operating as service and emergency braking devices,

the service braking device including a fluid pressure chamber having asupply connection providing for introduction of pressure fluid andhaving a reciprocable fluid pressure responsive wall element forimparting brake applying motion to the brake actuating member,

the equipment being characterized in that the emergency braking deviceincludes a fluid pressure chamber,

a reciprocable element forming a wall dividing the pressure chamber ofthe emergency device into two compartments,

said wall being movable in one direction to effect emergency applicationof the brake,

a supply connection normally providing for introduction of pressurefluid into that one of the compartments in which pressure acting on saidwall tends to move the wall in the other direction,

a passage interconnecting said two compartments,

and

an inlet valve in said passage positioned to provide for fluid flow fromsaid one compartment into the other but to prevent flow in the oppositedirection and thereby provide a force tending to move the dividing wallto apply the brake upon reduction of pressure in the compartment intowhich the supply of pressure fluid is normally introduced(.), and

check valve means in apassage interconnecting the two compartmentschecking air flow from one compartment into the other and permitting airflow in the opposite direction under certain conditions.

32. Brake operating equipment of the kind comprising a brake actuatingmember reciprocable in brake applying and brake releasing directions,

the brake operating equipment being divided into two sectionsrespectively operating as service and emergency braking devices,

the service braking device including a fluid pressure chamberhaving asupply connection providing for introduction of pressure fluid; andhaving a reciprocable fluid pressure responsive wall ele-.

two compartments, said wall being movable in one direction to effectemergency application of the brake,

a spring acting on said wall to urge itto move in said one direction,

a supply connection normally providing for introduction of pressurefluid into that one of the compartments in which pressure acting on saidwall tends to move the wall in the other direction to thereby providefor compression of said spring,

passage interconnecting said two compartments, and an inlet valve insaid passage positioned and so functioning as to provide for fluidflowfrom said one compartment into the other when, and only when, thefluid pressure in said compartment exceeds a predetermined level whichis beyond that required to compress the power spring,

but to prevent flow in the opposite direction and thereby provide aforce tending to move the dividing wall to apply the brake uponreduction of pressure in the compartment into which the supply ofpressure fluid is normally introduced.

33. A device as in claim 32 including check valve means in a passageinterconnecting saidtwo compartments checking air flow fromone'compartment into the other and permitting air flow in oppositedirection under certain conditions.

34. Brake operating equipment ofthe kind comprising a brake actuatingmember reciprocable in brake applying and brake releasing directions,

the brake operating equipment being divided into two sectionsrespectively operating as service and emergency braking devices,

the service braking device including a fluid pressure chamber having asupply connection providing for introduction of pressure fluid andhaving a reciprocable fluid pressure responsive vwall element forimparting brake applying motion to the brake actuating member,

the equipment'being characterized in that the emergency braking deviceincludes a fluid pressure chamber,

a reciprocable element forming a wall dividing the pressure chamber ofthe emergency device into two compartments, said wall being movable inone direction to effect emergency application of the brake,

a spring acting on said wall to urge it to move in said one direction,

a supply connection normally providing for introduction of pressurefluid into that one of the compartments in which pressure acting on saidwall tends to move the wall in the other direction to thereby providefor compression of said spring,

a passage interconnecting said two compartments, and an inlet valve insaid passage positioned to provide for fluid flow from said onecompartment into the other but to prevent flow in the opposite directionand thereby provide a force tending to move the dividing wall to applythe brake upon reduction of pressure in the compartment into which thesupply of pressure fluidis normally introduced(.) and a vent valve fromone of said compartments operative to vent pressure from saidcompartment to atmosphere outside thereof at a predetermined pressurelevel within said compartment.

1. In a brake actuating device having spring emergency and parkingfunctions and having operable connection with the braking mechanism of amotor vehicle and comprising, a closed housing divided into inner andouter compartments, a flexible diaphragm peripherally secured in theouter compartment, a brake operating rod surmounted by a diaphragmabutment plate extending axially through the inner and outercompartments and having attachment to the braking mechanism, a movablewall mounted within the inner compartment equipped with a tubular axialextension surrounding and having abutting engagement at its inner endwith said rod, an annular member forming the partition between the innerand outer compartments, a power compression spring unit between saidannular member and movable wall, a rod return compression spring betweenthe diaphragm abutment plate and annular member, separate air inlets forintroducing compressed air to the inner compartment between the movablewall and the inner end of the housing and to the outer compartmentbetween the diaphragm and the outer end of the housing, the improvementswhich comprise said movable wall, centrally thereof, slidingly sealed inpressure retaining fashion to the brake operating rod, said annularmember also slidingly sealed in pressure retaining fashion to said brakeoperating rod, said annular member and movable wall seals on the brakeoperating rod, together with the member and wall, defining therebetweena sealed air assist chamber, the tubular axial extension of the movablewall extending through the inner end of the housing in sliding sealedfashion whereby to define peripherally thereof within the housing andbetween the inner end of the housing and the inner face of the movablewall a movable wall pressurization chamber, at least one passage throughsaid movable wall having inlet valve means permitting air flow from themovable wall pressurization chamber into the air assist chamber when thepressure in the movable wall pressurization chamber reaches a certainpredetermined level, and check valve means therein checking flow fromthe movable wall pressurization chamber into the air assist chamber andpermitting flow in opposite direction under Certain conditions.
 2. Abrake actuating device as in claim 1 including a vent valve from the airassist chamber exterior of said closed housing operative to ventpressure from said air assist chamber outside of said housing at apredetermined pressure level within said air assist chamber.
 3. A deviceas in claim 1 wherein the check valve means and the inlet valve meansthrough the movable wall communicating between the air assist chamberand the movable wall pressurization chamber are positioned withinseparate passages through said movable wall.
 4. In combination, ahousing, said housing having inner and outer ends with respect to avehicle brake mechanism, one end of said housing closed by an inner wallmember having a central opening therethrough, the other end of saidhousing closed by an outer wall member, a movable wall within saidhousing with the outer face thereof next to the outer wall member ofsaid housing, coil compression spring means seating between said movablewall outer face and housing outer wall member, a rod connected at oneend thereof centrally of said movable wall, extending inwardly of thelatter and having a sliding fit through the inner wall member centralopening, an air inlet into said housing between the inner wall memberand the inner face of the movable wall whereby to permit pressurizationof a movable wall pressurization chamber defined between said movablewall and inner wall member, the movable wall outer face and outer wallmember defining therebetween an air assist chamber, at least one openingthrough said movable wall communicating from said movable wallpressurization chamber to said air assist chamber and having inlet feedvalve means operative at a predetermined pressure level to pass airpressure from said movable wall pressurization chamber into said airassist chamber, and check valve means therein checking flow into the airassist chamber and permitting flow therefrom under certain conditions.5. A device as in claim 4 including a relief valve in said outer wallmember operative to relieve the air assist chamber defined between themovable wall outer face and outer wall member at a predeterminedpressure therein.
 6. A device as in claim 4 wherein the check valvemeans and the inlet valve means through the movable wall communicatingbetween the air assist chamber and the movable wall pressurizationchamber are positioned within separate passages through said movablewall.
 7. Brake actuating mechanism comprising a closed housing havinginner and outer walls, said walls inner and outer with respect to avehicle brake mechanism, a flexible diaphragm within said housingperipherally secured in place, means for introducing fluid underpressure to said housing adjacent the outer wall thereof and on theouter side of said diaphragm, a brake operating rod on the other, innerside of said diaphragm axially arranged relative thereto, said rodprojecting through the inner end wall of the housing for reciprocatorymovements, a pad on the outer end of said brake or rod operable to bearagainst said diaphragm an auxiliary compartment at one end of saidhousing, the outer end wall of said housing constituting the inner endwall of said compartment, the inner end wall of the compartment having acentral opening therethrough, the outer end of said compartment closedby an outer wall member, a movable wall within said compartment with theouter face thereof facing the outer wall of said compartment, coilcompression spring means seating between said movable wall outer faceand compartment outer wall member, a rod connected centrally with saidmovable wall, extending inwardly thereof and having a sliding fitthrough the housing outer end wall central opening, means forintroducing fluid under pressure to said compartment adjacent to thehousing outer wall for normally holding the movablE wall in the regionof the compartment outer wall thereby to hold said coil compressionspring means under compression, said fluid under pressure introducedinto a movable wall pressurization chamber between the movable wallinner face and the housing outer wall outer face, at least one passagethrough said movable wall connecting the movable wall pressurizationchamber and the air assist chamber with check valve means thereinchecking flow from the movable wall pressurization chamber to the airassist chamber while permitting flow in the other direction undercertain pressurization conditions and inlet valve means operative topass fluid under pressure from the movable wall pressurization chamberto the air assist chamber when the pressure level within the movablewall pressurization chamber rises above a predetermined level.
 8. Abrake actuating mechanism as in claim 7 including a vent valve in theouter end wall of said compartment operative to vent the air assistchamber defined by the movable wall outer face and the inner face of thecompartment outer wall.
 9. A device as in claim 7 wherein the checkvalve means and the inlet valve means through the movable wallcommunicating between the air assist chamber and the movable wallpressurization chamber are positioned within separate passages throughsaid movable wall.
 10. In a brake actuating device having springemergency and parking functions, operable connection with the brakingmechanism of a vehicle and comprising, a closed housing divided intoinner and outer compartments, a flexible diaphragm peripherally securedin the outer compartment, a brake operating rod surmounted by adiaphragm abutment plate extending axially through the inner and outercompartments and having attachment to the braking mechanism, a movablewall mounted within the inner compartment equipped with a tubular axialextension surrounding and having abutting engagement at its inner endwith said rod, an annular member forming the partition between the innerand outer compartments, a power compression spring unit between saidannular member and movable wall, a rod return compression spring betweenthe diaphragm abutment plate and annular member, separate air inlets forintroducing compressed air to the inner compartment between the movablewall and the inner end of the housing and to the outer compartmentbetween the diaphragm and the outer end of the housing, the improvementswhich comprise said movable wall, centrally thereof, slidingly sealed inpressure retaining fashion to the brake operating rod, said annularmember also slidingly sealed in pressure retaining fashion to said brakeoperating rod, said annular member and movable wall seals on the brakeoperating rod, together with the member and wall, defining therebetweena sealed air assist chamber, the tubular axial extension of the movablewall extending through the inner end of the housing in sliding sealedfashion, whereby to define peripherally thereof within the housing andbetween the inner end of the housing and the inner face of the movablewall a movable wall pressurization chamber, at least one air flowpassage having inlet valve means therewithin permitting air flow fromthe movable wall pressurization chamber into the air assist chamber,when the pressure in the movable wall pressurization chamber reaches acertain predetermined level.
 11. A device as in claim 10 including checkvalve means in a passage communicating between the movable wallpressurization chamber and air assist chamber checking air flow from themovable wall pressurization chamber into the air assist chamber andpermitting air flow in opposite direction under certain conditions. 12.A brake actuating device as in claim 10 including a vent valve from theair assist chamber exterior of said closed housing operative to ventpressure from said air assist chamber outside of said housing at apredetermined preSsure level within said air assist chamber.
 13. Adevice as in claim 10 wherein the check valve means and the inlet valvemeans communicating between the air assist chamber and the movable wallpressurization chamber are positioned within separate passages.
 14. Abrake actuating device as in claim 11 including a vent valve from theair assist chamber exterior of said closed housing operative to ventpressure from said air assist chamber outside of said housing at apredetermined pressure level within said air assist chamber.
 15. Incombination, a housing, said housing having inner and outer ends withrespect to a vehicle brake mechanism, one end of said housing closed byan inner wall member having a central opening therethrough, the otherend of said housing closed by an outer wall member, a movable wallwithin said housing with the outer face thereof next to the outer wallmember of said housing, coil compression spring means seating betweensaid movable wall outer face and housing outer wall member, a rodconnected at one end thereof centrally of said movable wall, extendinginwardly of the latter and having a sliding fit through the inner wallmember central opening, an air inlet into said housing between the innerwall member and the inner face of the movable wall, whereby to permitpressurization of a movable wall pressurization chamber defined betweensaid movable wall and inner wall member, the movable wall outer face andouter wall member defining therebetween an air assist chamber, and atleast one air flow passage communicating between said movable wallpressurization chamber and said air assist chamber and having inlet(feed) valve means positioned therein operative at a predeterminedpressure level to pass pressurized air from said movable wallpressurization chamber into said air assist chamber(.) when, and onlywhen, the fluid pressure in said chamber exceeds a predetermined levelwhich is beyond that required to compress the power spring, but toprevent flow in the opposite direction and thereby provide a forcetending to move the movable wall to apply the brake upon reduction ofpressure in the chamber into which the supply of pressure fluid isnormally introduced.
 16. A device as in claim 15 including check valvemeans in a passage communicating between the movable wall pressurizationchamber and air assist chamber checking air flow into the air assistchamber from the movable wall pressurization chamber and permitting airflow therefrom under certain conditions.
 17. In combination, a housing,said housing having inner and outer ends with respect to a vehicle brakemechanism, one end of said housing closed by an inner wall member havinga central opening therethrough, the other end of said housing closed byan outer wall member, a movable wall within said housing with the outerface thereof next to the outer wall member of said housing, coilcompression spring means seating between said movable wall outer faceand housing outer wall member, a rod connected at one end thereofcentrally of said movable wall, extending inwardly of the latter andhaving a sliding fit through the inner wall member central opening, anair inlet into said housing between the inner wall member and the innerface of the movable wall, whereby to permit pressurization of a movablewall pressurization chamber defined between said movable wall and innerwall member, the movable wall outer face and outer wall member definingtherebetween an air assist chamber, and at least one air flow passagecommunicating between said movable wall pressurization chamber and saidair assist chamber and having inlet feed valve means therein operativeat a predetermined pressure level to pass pressurized air from saidmovable wall pressurization chamber into said air assist chamber(.)check valve means in a passage communicating between the movable wallpressurization chAmber and air assist chamber checking air flow into theair assist chamber from the movable wall pressurization chamber andpermitting air flow therefrom under certain conditions, and (A device asin claim 20 including) a relief valve operative to relieve the airassist chamber defined between the movable wall outer face and outerwall member at a predetermined pressure therein.
 18. In combination, ahousing, said housing having inner and outer ends with respect to avehicle brake mechanism, one end of said housing closed by an inner wallmember having a central opening therethrough, the other end of saidhousing closed by an outer wall member a movable wall within saidhousing with the outer face thereof next to the outer wall member ofsaid housing, coil compression spring means seating between said movablewall outer face and housing outer wall member, a rod connected at oneend thereof centrally of said movable wall, extending inwardly of thelatter and having a sliding fit through the inner wall member centralopening, an air inlet into said housing between the inner wall memberand the inner face of the movable wall, whereby to permit pressurizationof a movable wall pressurization chamber defined between said movablewall and inner wall member, the movable wall outer face and outer wallmember defining therebetween an air assist chamber, and at least one airflow passage communicating between said movable wall pressurizationchamber and said air assist chamber and having inlet feed valve meanstherein operative at a predetermined pressure level to pass pressurizedair from said movable wall pressurization chamber into said air assistchamber(.), and (A device as in claim 19 including) a relief valveoperative to relieve the air assist chamber defined between the movablewall outer face and outer wall member at a predetermined pressuretherein.
 19. Brake actuating mechanism comprising a closed housinghaving inner and outer walls, said walls inner and outer with respect toa vehicle brake mechanism, a flexible diaphragm within said housingperipherally secured in place, means for introducing fluid underpressure to said housing adjacent the outer wall thereof and on theouter side of said diaphragm, a brake operating rod on the other, innerside of said diaphragm axially arranged relative thereto, said rodprojecting through the inner end wall of the housing for reciprocatorymovements, a pad on the outer end of said brake or rod operable to bearagainst said diaphragm, an auxiliary compartment at one end of saidhousing, the outer end wall of said housing constituting the inner endwall of said compartment, the inner end wall of the compartment having acentral opening therethrough, the outer end of said compartment closedby an outer wall member, a movable wall within said compartment with theouter face thereof facing the outer wall of said compartment, coilcompression spring means seating between said movable wall outer faceand compartment outer wall member, a rod connected centrally with saidmovable wall, extending inwardly thereof and having a sliding fitthrough the housing outer end wall central opening, means forintroducing fluid under pressure into a movable wall pressurizationchamber between the movable wall inner face and the housing outer wallouter face, thus normally holding the movable wall in the region of thecompartment outer wall thereby to hold said coil compression springmeans under compression, a passage interconnecting the movable wallpressurization chamber and the air assist chamber; inlet valve means insaid passage so positioned and so functioning as to pass fluid underpressure from the movable wall pressurization chamber to the air assistchamber when and only when the pressure level within the movable wallpressurization chamber rises above a predetermined level which is beyondthAt required to compress the power spring, but to prevent flow in theopposite direction and thereby provide a force tending to move thedividing wall to apply the brake upon reduction of pressure in thecompartment into which the supply of pressure fluid is normallyintroduced.
 20. A device as in claim 19 including check valve means in apassage interconnecting the movable wall pressurization chamber and theair assist chamber checking air flow from the movable wallpressurization chamber to the air assist chamber while permitting airflow in the other direction under certain pressurization conditions. 21.A brake actuating mechanism as in claim 19 including a vent valveoperative to vent to atmosphere the air assist chamber (defined by themovable wall outer face and the inner face of the compartment outerwall) at a predetermined pressure level therein.
 22. In a brakeactuating device having emergency and parking functions, operableconnection with the braking mechanism of a vehicle and comprising, aclosed housing divided into inner and outer compartments, a flexiblediaphragm peripherally secured in the outer compartment, a brakeoperating rod surmounted by a diaphragm abutment plate extending axiallythrough the inner and outer compartments and having attachment to thebraking mechanism, a movable wall mounted within the inner compartmentequipped with a tubular axial extension surrounding and having abuttingengagement at its inner end with said rod, an annular member forming thepartition between the inner and outer compartments, a rod returncompression spring between the diaphragm abutment plate and annularmember, separate air inlets for introducing compressed air to the innercompartment between the movable wall and the inner end of the housingand to the outer compartment between the diaphragm and the outer end ofthe housing, the improvements which comprise said movable wall,centrally thereof, slidingly sealed in pressure retaining fashion to thebrake operating rod, said annular member also slidingly sealed inpressure retaining fashion to said brake operating rod, said annularmember and movable wall seals on the brake operating rod, together withthe member and wall, defining therebetween a sealed air assist chamber,the tubular axial extension of the movable wall extending through theinner end of the housing in sliding sealed fashion, whereby to defineperipherally thereof within the housing and between the inner end of thehousing and the inner face of the movable wall a movable wallpressurization chamber, at least one air flow passage having inlet valvemeans therewithin permitting air flow from the movable wallpressurization chamber into the air assist chamber, when the pressure inthe movable wall pressurization chamber reaches a certain predeterminedlevel.
 23. A device as in claim 22 including check valve means in apassage communicating between the movable wall pressurization chamberand air assist chamber checking air flow from the movable wallpressurization chamber into the air assist chamber and permitting airflow in opposite direction under certain conditions.
 24. A device as inclaim 22 including a vent valve from the air assist chamber exterior ofsaid closed housing operative to vent pressure from said air assistchamber outside of said housing at a predetermined pressure level withinsaid air assist chamber.
 25. A device as in claim 22 wherein the checkvalve means and the inlet valve means communicating between the airassist chamber and the movable wall pressurization chamber arepositioned within separate passages.
 26. In combination, a housing, saidhousing having inner and outer ends with respect to a vehicle brakemechanism, one end of said housing closed by an inner wall member havinga central opening therethrough, the other end of said housing closed byan outer wall member, a movable wall withIn said housing with the outerface thereof next to the outer wall member of said housing, a rodconnected at one end thereof centrally of said movable wall, extendinginwardly of the latter and having a sliding fit through the inner wallmember central opening, an air inlet into said housing between the innerwall member and the inner face of the movable wall, whereby to permitpressurization of a movable wall pressurization chamber defined betweensaid movable wall and inner wall member, the movable wall outer face andouter wall member defining therebetween an air assist chamber, at leastone air flow passage communicating between said movable wallpressurization chamber and said air assist chamber and having inlet feedvalve means positioned therein and so functioning as to be operative ata predetermined pressure level to pass pressurized air from said movablewall pressurization chamber into said air assist chamber(.) when, andonly when, the fluid pressure in said compartment exceeds apredetermined level which is beyond that required to compress the powerspring, but to prevent flow in the opposite direction and therebyprovide a force tending to move the dividing wall to apply the brakeupon reduction of pressure in the compartment into which the supply ofpressure fluid is normally introduced.
 27. A device as in claim 26including check valve means in a passage communicating between themovable wall pressurization chamber and air assist chamber checking airflow into the air assist chamber from the movable wall pressurizationchamber and permitting air flow therefrom under certain conditions. 28.A device as in claim 26 including a (relief) vent valve operative torelieve to atmosphere the air assist chamber (defined between themovable wall outer face and outer wall member of the) at a predeterminedpressure level therein.
 29. Brake operating equipment of the kindcomprising a brake actuating member reciprocable in brake applying andbrake releasing directions, the brake operating equipment being dividedinto two sections respectively operating as service and emergencybraking devices, the service braking device including a fluid pressurechamber having a supply connection providing for introduction ofpressure fluid and having a reciprocable fluid pressure responsive wallelement for imparting brake applying motion to the brake actuatingmember, the equipment being characterized in that the emergency brakingdevice includes a fluid pressure chamber, a reciprocable element forminga wall dividing the pressure chamber of the emergency device into twocompartments, said wall being movable in one direction to effectemergency application of the brake, a supply connection normallyproviding for introduction of pressure fluid into that one of thecompartments in which pressure acting on said wall tends to move thewall in the other direction, a passage interconnecting said twocompartments, and an inlet valve in said passage positioned and sofunctioning as to provide for fluid flow from said one compartment intothe other when, and only when, the fluid pressure in said compartmentexceeds a predetermined level which is beyond that required to compressthe power spring, but to prevent flow in the opposite direction andthereby provide a force tending to move the dividing wall to apply thebrake upon reduction of pressure in the compartment into which thesupply of pressure fluid is normally introduced.
 30. A device as inclaim 29 including a vent valve from one of said compartments exteriorto atmosphere thereof operative to vent pressure therefrom at apredetermined pressure level within said compartment.
 31. Brakeoperating equipment of the kind comprising a brake actuating memberreciprocable in brake applying and brake releasing directions, the brakeoperating equipment being divided into two sections respectivelyoperating as service and emergency brAking devices, the service brakingdevice including a fluid pressure chamber having a supply connectionproviding for introduction of pressure fluid and having a reciprocablefluid pressure responsive wall element for imparting brake applyingmotion to the brake actuating member, the equipment being characterizedin that the emergency braking device includes a fluid pressure chamber,a reciprocable element forming a wall dividing the pressure chamber ofthe emergency device into two compartments, said wall being movable inone direction to effect emergency application of the brake, a supplyconnection normally providing for introduction of pressure fluid intothat one of the compartments in which pressure acting on said wall tendsto move the wall in the other direction, a passage interconnecting saidtwo compartments, and an inlet valve in said passage positioned toprovide for fluid flow from said one compartment into the other but toprevent flow in the opposite direction and thereby provide a forcetending to move the dividing wall to apply the brake upon reduction ofpressure in the compartment into which the supply of pressure fluid isnormally introduced(.), and check valve means in a passageinterconnecting the two compartments checking air flow from onecompartment into the other and permitting air flow in the oppositedirection under certain conditions.
 32. Brake operating equipment of thekind comprising a brake actuating member reciprocable in brake applyingand brake releasing directions, the brake operating equipment beingdivided into two sections respectively operating as service andemergency braking devices, the service braking device including a fluidpressure chamber having a supply connection providing for introductionof pressure fluid and having a reciprocable fluid pressure responsivewall element for imparting brake applying motion to the brake actuatingmember, the equipment being characterized in that the emergency brakingdevice includes a fluid pressure chamber, a reciprocable element forminga wall dividing the pressure chamber of the emergency device into twocompartments, said wall being movable in one direction to effectemergency application of the brake, a spring acting on said wall to urgeit to move in said one direction, a supply connection normally providingfor introduction of pressure fluid into that one of the compartments inwhich pressure acting on said wall tends to move the wall in the otherdirection to thereby provide for compression of said spring, a passageinterconnecting said two compartments, and an inlet valve in saidpassage positioned and so functioning as to provide for fluid flow fromsaid one compartment into the other when, and only when, the fluidpressure in said compartment exceeds a predetermined level which isbeyond that required to compress the power spring, but to prevent flowin the opposite direction and thereby provide a force tending to movethe dividing wall to apply the brake upon reduction of pressure in thecompartment into which the supply of pressure fluid is normallyintroduced.
 33. A device as in claim 32 including check valve means in apassage interconnecting said two compartments checking air flow from onecompartment into the other and permitting air flow in opposite directionunder certain conditions.
 34. Brake operating equipment of the kindcomprising a brake actuating member reciprocable in brake applying andbrake releasing directions, the brake operating equipment being dividedinto two sections respectively operating as service and emergencybraking devices, the service braking device including a fluid pressurechamber having a supply connection providing for introduction ofpressure fluid and having a reciprocable fluid pressure responsive wallelement for imparting brake applying motion to the brake actuatingmember, the equipment being characterized in that the emergency brakingdEvice includes a fluid pressure chamber, a reciprocable element forminga wall dividing the pressure chamber of the emergency device into twocompartments, said wall being movable in one direction to effectemergency application of the brake, a spring acting on said wall to urgeit to move in said one direction, a supply connection normally providingfor introduction of pressure fluid into that one of the compartments inwhich pressure acting on said wall tends to move the wall in the otherdirection to thereby provide for compression of said spring, a passageinterconnecting said two compartments, and an inlet valve in saidpassage positioned to provide for fluid flow from said one compartmentinto the other but to prevent flow in the opposite direction and therebyprovide a force tending to move the dividing wall to apply the brakeupon reduction of pressure in the compartment into which the supply ofpressure fluid is normally introduced(.) , and a vent valve from one ofsaid compartments operative to vent pressure from said compartment toatmosphere outside thereof at a predetermined pressure level within saidcompartment.